Cryo-shucking of oysters

ABSTRACT

A cryogen-blanching technique involves brief exposure of an oyster shell to a cryogen. The cryo-blanching weakens the oyster&#39;s muscles that close the bivalve tightly shut, but preserves the natural condition of the bulk of the oyster meat. The weakening of the oyster&#39;s holding muscles allows shucking the oyster meat in its fresh or natural state without damage or shell fragments.

TECHNICAL FIELD

The present application relates, in general, to culinary science andfood processing technology. In particular, the application relates totechniques for shucking oysters.

BACKGROUND

Oyster is used as a common name for a number of distinct groups ofbivalve mollusks, which live in marine or brackish habitats. Oysters arean important food source in coastal areas, and oyster fisheries are animportant commercial industry. See e.g., websiteen.wikipedia.org/wiki/Oyster.

The bivalve shells of live oysters are normally tightly closed.Individual oysters can be round or more commonly oval in shape (FIG. 1).One of the valves (half-shell) is generally more rounded or convex thatthe other half-shell. This rounded half-shell is commonly referred to asthe cupped half-shell. The other half-shell, which is flatter, acts as alid over the cupped half-shell. A single powerful oyster muscle—theadductor muscle, which is attached to the cupped half-shell, holds thetwo half-shells shut tightly. The two half-shells are also joined at ahinge joint located at the circumference of the shell by a hinge muscle.

FIG. 2, which is adapted from the website oysters.us/opening.html, showstopographic features or regions that are common to all oyster shapes.The beak portion is the pointed part of any oyster. The beak portion isshown pointing toward the bottom of the FIG. 2. The oyster's hinge jointmuscle is found immediately above the beak. The lip or bill is the broadflat end vertically opposite the beak. The oyster's adductor muscle isgenerally found to the right of the median axis running from the beak tothe bill, slightly above midpoint (i.e. in the upper right quadrant asshown in FIG. 2).

Oysters must be eaten alive, or cooked alive. Shucking, refers toprocess of removing of the oyster meat from the tightly-closed bivalveshell of an oyster. Shucking oysters is usually accomplished manually byhand. A mechanical tool, e.g., a shortbladed oyster knife, is insertedbetween the two halves of the bivalve shell, close to the hinge, andtwisted to break the hinge and lever the oyster half-shells apart. Theknife is then used to sever the adductor muscle at its point ofattachment to the cupped half, and the oyster meat removed. If the meatis to be served on the half-shell, the detached meat is turned over,cleared of any shell fragments, and left in the cupped half-shell alongwith the natural liquor. See e.g., FIG. 3 and websitesmarylandinfo.com/sponsorships/how_to_shuck_oysters.htmlfao.org/wairdocs/tan/x5954e/x5954e01.htm.

The manual process of shucking oysters is labor intensive.Labor-reducing techniques that are deployed in the commercialfood-processing industry for shucking oysters may include shearing offthe hinge (e.g., by guillotine) and a wide range of treatments (e.g.,chemicals, heat, cold, vacuum, microwave and laser treatments) thatcause the shell to spring open. All these common commercial treatmentsthat cause the oyster shell to self-open affect the freshness, integrityand quality of the oyster meat that is scraped out from the self-openedshell.

Attention is now directed to improved or different techniques forshucking oysters.

BRIEF DESCRIPTION OF THE FIGURES

In the accompanying drawings:

FIG. 1 is an illustration of an oval-shaped oyster;

FIG. 2 is an illustration of an oyster half-shell. The figure identifiescommon topographic features and geometries found in most oysters;

FIG. 3 illustrates the steps involved in shucking an oyster manually byhand. FIG. 3 is adapted from “how to shuck oysters” at websiteMarylandinfo.com;

FIG. 4 is a flow diagram illustrating an exemplary method for shuckingoysters involving pre-treatment of the oysters with a cryogen, inaccordance with the principles of the solutions described herein; and

FIG. 5 is a flow diagram illustrating another exemplary method forshucking oysters involving cryo-blanching the oysters, in accordancewith the principles of the solutions described herein.

Throughout the figures, unless otherwise stated, the same referencenumerals and characters are used to denote like features, elements,components, or portions of the illustrated embodiments.

DESCRIPTION

Oyster shucking techniques are described herein. The techniques involveuse of cryogens to pre-treat oysters. In particular, the techniques mayinvolve localized treatment of oyster muscles with cryogens. The coolingor freezing of the oyster muscles weakens them. Therefore, themechanical forces that are required to shuck oysters treated withcryogens in the manner described herein are substantially less thanthose compared to those required to shuck untreated oysters. Oystersthat are suitably cryogen-treated are shucked easily and cleanly.

Specific examples of methods for treating oysters with cryogens prior toshucking are described herein with reference to FIGS. 4 and 5. It willbe understood that these examples are presented only for purposes ofillustration and are not intended to limit the scope of the disclosure.

FIG. 4 shows method 400 for cryo-shucking oysters. Method 400 includesproviding an oyster in a bivalve shell, wherein the shell has a cuppedhalf-shell and a lid half-shell that are held shut by the oyster's hingemuscle about a beak portion of the bivalve shell (410), and applying acryogen to the beak portion to substantially cool or freeze the oyster'shinge muscle (420). Any suitable or convenient cryogen may be used(e.g., liquid nitrogen, dry ice., etc). The cryogen may be appliedlocally, for example, by directing a fluid cryogen stream on to the beakportion of the bivalve shell: Alternatively, the oyster's beak portionmay be dipped in a fluid cryogen or otherwise placed in contact withcryogens to freeze only the hinge muscle portion. A batch of oysters maybe treated at the same time, for example, placing a suitably orientingthe batch (e.g., vertically as shown in FIG. 2). The beak portion may bein contact with the cryogen for a limited amount of time that issufficient to freeze the hinge muscle only. This limited amount of timemay be a function of the cryogen type (e.g. liquid nitrogen or dry ice,etc.) and the cryogen temperatures and the type of oyster shell. Theamount of exposure time necessary may be determined empirically. Theamount of time that the oyster is in contact with the cryogen issuitably limited so that only the hinge muscle is frozen and that tooonly briefly. The brief freezing of the hinge muscle likely alters themuscle's structure to weaken its elasticity and grip on the half-shellswithout altering or affecting the texture and taste of the remainder ofthe oyster flesh.

Method 400 further includes the step of removing the lid or flathalf-shell (430). The lid half-shell may be removed by sliding it openrelative to the cupped half-shell. Alternatively, the weakened hingemuscles may relax naturally allowing the half-shells to self-open.

Example I

In an example, in the inventors' kitchen a batch of oysters was washedin warm water and then dipped in liquid nitrogen for about 10-15seconds. The oysters were then washed in warm water to thaw the surface.In traditional or conventional cooking term “blanching,” which involvesplunging a food substance into boiling water and removing it after abrief, timed interval. In analogy, the cooling or freezing of the oystermuscle by a brief time-limited exposure to the cryogen may be referredto herein as “cryo-blanching.” In the foregoing example, thecryo-blanched oysters were place on a rack in an ordinary kitchenrefrigerator where they self-opened in a few hours. The cryo-blanchingtreatment had sufficiently altered the structure of the hinge muscles sothat they relaxed naturally to open up the half-shells. The oyster meatin the opened half-shell was in its natural tender and juicy state. Thenatural shape of the oyster meat was undisturbed. The oyster meat wasremoved by sliding a blade under oyster meat to sever the adductormuscle or knob attaching it the cupped half-shell.

FIG. 5 shows method 500 for cryo-shucking oysters. Method 500 includesproviding an oyster in a bivalve shell, wherein the shell has a cuppedhalf-shell and a lid half-shell that are held shut by the oyster's hingemuscle about a beak portion of the bivalve shell that is opposite a billportion of thereof, and wherein oyster meat is attached to the cuppedhalf-shell by the oyster's adductor muscle to weaken its grip (510);applying a cryogen locally to substantially cool or freeze the oyster'sadductor muscle to weaken its grip (520); opening the oyster's lidhalf-shell relative to the cupped half-shell to expose the oyster meat(530); and detaching the oyster meat form the cupped half-shell (540).In method 500 for cryo-shucking an oyster, the adductor muscle may beweakened by applying cryogen to the entire oyster shell or locally tothe backside of cupped half-shell. The latter may be accomplished, forexample, by placing the oysters' cupped-side down on a bed of dry ice orin shallow tray of liquid nitrogen or other cryogen. The oyster shell,submerged or partially submerged, is contact with the cryogen for only alimited amount of time so that bulk of the oyster meat is not frozen,but only the outer portions close to and in immediate thermal contactwith the shell walls (e.g., the adductor and/or hinge muscle portions)are substantially cooled.

Example II

In another example, in the inventors' kitchen a batch of oysters waswashed in warm water and the dipped in liquid nitrogen for about 30-90seconds. The oysters were then washed in warm water to thaw the surface.The cryo-blanched oysters were placed on a rack in an ordinary kitchenrefrigerator, where they self-opened in a few hours. The cryo-blanchingtreatment had sufficiently altered the structure of the hinge musclesthat they relaxed naturally to open up the half-shells. The oyster meatin the opened half-shell was in its natural tender and juicy state. Thenatural shape of the oyster meat was undisturbed. Further, thecryo-blanching had weakened the adductor muscle allowing the oyster meatto be easily scooped out of the cupped half-shelf using a spoon andflipped over for the oyster serving in half-shell. The shucked oystermeat was raw and juicy. Further, the oyster meat had firmer and denserfeeling than that of conventionally shucked oyster meat.

The oyster shucking methods described herein may be exploited to preparesmall quantities (e.g., individual food servings prepared in homekitchens) and/or large quantities (e.g., commercial food servingsprepared in industrial kitchens or other commercial food processingindustry).

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.For example, in Examples I and II, instead of waiting for thecryo-blanched shells to self-open shells, the covering flat half-shellsmay be manually slid off, physically lifted, or otherwise removed toexpose the oyster meat contained in the cupped half-shell.

Further, in some industrial oyster processing the beak or other edgeportion of the oyster shell is guillotined or sheared off to create anopening. In such processing, an alternative to cooling the adductormuscle through the shell wall as described above, is to apply a cryogendirectly to the adductor muscle. The cryogen may be introduced throughthe sheared opening into a region proximate to the adductor muscle'sattachment to the inner surface of the shell wall. Such cryo-treatmentof the adductor muscle may loosen its grip on the shell wall and allowfor easy removal of the oyster meat.

It will be understood that the various aspects and embodiments disclosedherein are for purposes of illustration and are not intended to belimiting, with the true scope and spirit being indicated by thefollowing claims. For example, liquid nitrogen treatment may be used toopen or shuck other shell fish (e.g., clams).

1. A method for shucking oysters, comprising: providing an oyster in abivalve shell, wherein the shell has a cupped half-shell and a lidhalf-shell that held together by the oyster's hinge muscle about a beakportion or hinge joint of the bivalve shell; applying a cryogen to thebeak portion to substantially cool or freeze the hinge muscle; andremoving or opening the lid half-shell relative to the cupped half-shellto expose the oyster meat.
 2. The method of claim 1, wherein the cryogenis dry ice.
 3. The method of claim 1, wherein the cryogen is liquidnitrogen.
 4. The method of claim 3, wherein applying the cryogen to thebeak portion to substantially cool or freeze the hinge muscle comprisesdipping oyster in liquid nitrogen for only short time interval so thatthe bulk of the oyster meat remains unfrozen.
 5. The method of claim 4,wherein applying the cryogen to the beak portion to substantially coolor freeze the hinge muscle comprises dipping oyster in liquid nitrogenfor about 10-15 seconds.
 6. The method of claim 1, further comprising,removing the oyster meat from the cupped half-shell.
 7. The method ofclaim 6, wherein removing the oyster meat comprises sliding a bladeunder oyster meat in the cupped half-shell.
 8. The method of claim 6,wherein sliding the blade under oyster meat in the cupped half-shellcomprises cutting the oyster's adductor muscle that is attached to thecupped half-shell.
 9. A method for shucking oysters, comprising:providing an oyster in a bivalve shell, wherein the shell has a cuppedhalf-shell and a lid half-shell that are held shut by the oyster's hingemuscle about a beak portion of the bivalve shell that is opposite a billportion thereof, and wherein oyster meat is attached to an inner surfaceof the cupped half-shell by the oyster's adductor muscle; cooling theadductor muscle to weaken attachment of the oyster meat to the innersurface of the cupped half-shell; opening the hinged lid half-shell andcupped half-shell about the bill portion of the bivalve shell; anddetaching the oyster meat from the cupped half-shell.
 10. The method ofclaim 1, wherein cooling the adductor muscle comprises applying acryogen to the oyster to cool the adductor muscle.
 11. The method ofclaim 10, wherein the cryogen is dry ice.
 12. The method of claim 10,wherein the cryogen is liquid nitrogen.
 13. The method of claim 12,wherein applying the cryogen to the oyster to cool the adductor musclecomprises dipping the oyster in liquid nitrogen for an only short timeinterval so that the bulk of the oyster meat remains unfrozen.
 14. Themethod of claim 13, wherein applying the cryogen to the oyster to coolthe adductor muscle comprises dipping the oyster in liquid nitrogen forabout 30-90 seconds.
 15. The method of claim 10, wherein cooling theadductor muscle comprises applying a cryogen to an external surfaceportion of the cupped half-shell.
 16. The method of claim 10, furthercomprising, slicing an edge portion of the bivalve shell to make anopening, and wherein cooling the adductor muscle comprises injecting acryogen through the opening into a region proximate to the adductormuscle's attachment to the cupped half-shell.
 17. The method of claim 9,further comprising, detaching the oyster meat from the cuppedhalf-shell.
 18. The method of claim 17, wherein detaching the oystermeat from the cupped half-shell comprises scooping the oyster meat inthe cupped half-shell using a spoon.
 19. The method of claim 17, whereindetaching the oyster meat from the cupped half-shell comprises sliding ablade under oyster meat in the cupped half-shell to sever the adductormuscle.